Using Mass Balance to Understand Atmospheric CFCs

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Summary

Students use an interactive online mass balance model to help understand the observed levels of chlorofluorocarbon CFC-12 over the recent past. They then explore the influence of post Montreal Protocol emission scenarios on future CFC levels and discuss the relevance of this to stratospheric ozone recovery.

Learning Goals

Use a model to estimate the future concentrations of CFC-12 under several different assumed emission scenarios.

Learn how a mass balance model applies to the global atmosphere.

Understand how atmospheric lifetime is related to the response time of atmospheric constituents.

Calibrate a model with recent observations.

Synthesize results into a well written summary.

Accurately read graphical information.

Read and interpolate data from a table of values.

Context for Use

This activity is useful in any course with a section on atmospheric trace gases and/or stratospheric ozone. It has been used successfully in an introductory meteorology course as well as an upper division course on Earth's Climate for non-majors.

Teaching Notes and Tips

This activity works best with a PC, but with proper configuration also works on MAC OS X.

Little mathematical background is required to complete this activity.

Here are some suggestions for effective classroom use and more details of the mathematics behind the model.

Also see References and Resources below.

Assessment

Grading the completed activity sheet provided below can be used as an assessment of student understanding. Follow-up discussions in class, essay questions on exams, and the future success of students on other related activities are also useful measures of student understanding.

References and Resources

The activity "Using Mass Balance to Understand Atmospheric Levels of CFCs" described here is the third part of a four part learning module that I use in my courses when discussing Earth's Climate and Stratospheric Ozone.